1. Field of Use
This invention relates generally to relatively large manually operated leak-proof and corrosion-proof shut-off or stop valves for handling high pressure liquids and/or gases such as are used in refrigeration systems or the like.
In particular, the invention relates to means for securing a valve disc to the inner end of a valve spindle which extends into the valve body.
2. Description of the Prior Art
Large industrial and commercial refrigeration systems employ refrigerants, such as ammonia, freon and the like, which are circulated through the system at high pressure in gaseous and liquid form. These refrigerants are costly (presently as much as $12.00 per pound) and any leakage in a large system not only reduces system efficiency but adds to cost of operation. Such systems require relatively large manually operable shut-off or stop valves to control fluid flow. Heretofore, such valves typically comprised a one-piece cast iron valve body with integrally formed threaded inlet and outlet flow tubes to which threaded pipe ends were connected. A rotatable valve spindle with a handle wheel on its outer end and a valve disc on its inner end extended from the valve body. Various types of valve spindle stuffing box arrangements were employed to seal against leakage of high pressure past the valve spindle. Also, various valve seating arrangements were employed to ensure proper valve closure. Threaded connections on the valve body very often proved to be prone to fluid loss. Furthermore, valve seat and valve disc designs and valve spindle stuffing box designs--often dictated by the configuration of a cast iron valve body--were susceptible to wear requiring servicing and replacement. Again, prior art valve designs often required substantial disassembly of the valve to enable servicing and part-replacement. Typically, disassembly of the stuffing box for the valve spindle first required removal of the hand-wheel from the valve spindle. Not uncommonly, the hand-wheel was force-fitted in place and its removal required use of a wheel or bearing puller. The following U.S. Patents illustrate the state of the art and show various attempts to avoid the use of threaded cast-iron valve housings to provide improved valve structures, to improve valve seals, to facilitate repairs and to employ technology aimed at cost reduction. U.S Pat. Nos. 3,743,246 and 4,265,427 show gate valve bodies using geometrically shaped welded sections; U.S. Pat. Nos. 3,580,268, 3,678,556 and 3,518,742 are of a similar thrust; U.S. Pat. Nos. 3,523,551, 3,275,290, 4,322,058 and 3,337,183 concern stuffing box arrangements for valve stems.